The invention relates to novel synthetic derivatives of two thymic hormones, i.e. thymulin and thymosin, and to their uses as a medicament or in the field of cosmetology.
The large number of studies which have been carried out on the functioning of the immune system have demonstrated the cardinal role played by the thymus and the thymic hormones in stimulating the immune defences of the organism.
The thymic hormones, in particular thymulin, "J. F. Bach et al.", thymopoietin "Grandstein" and thymosin "Dayne" have been identified as being of a polypeptide or peptide nature.
These hormones, principally thymulin and thymopoietin, possess the property of inducing maturation of the T lymphocytes and of stimulating the immune response of the organism.
It has been scientifically demonstrated that a close relationship exists between the decrease in thymic functions with age and cutaneous ageing under normal physiological circumstances.
At a pathological level, the loss of thymic activity, i.e. "involution", finds expression in the appearance of physiological disorders: "autoimmune diseases, alopecias (abnormal hair loss), etc.".
It has also been shown that a relationship exists between the physiological properties of the thymus and certain cells of the epidermis.
Thus, a structural similarity exists between certain cells of the thymus and keratinocytes. It has also been shown that, under certain conditions, the keratinocytes also secrete a hormone of the thymopoietin type which is identical to that secreted by the thymus and are able to induce post-thymic lymphocyte maturation and in this way to take over from the thymus.
This relationship between the physiological activities of the cells of the thymus and the keratinocytes has recently been confirmed by demonstrating that keratin and keratohyalin, which have identical structures to those of the keratin and keratohyalin which are secreted by the epidermal keratinocytes, are present in the cells of the thymus.
Furthermore, the scientific demonstration that keratinocytes which are in the differentiation phase secrete a substance, i.e. ETAF, which activates thymocyte growth, confirms the physiological relationships which exist between the thymus and the keratinocytes. (ETAF: epidermal thymocyte activating factor).
A parallel exists between the "involution" of the thymus and the decrease in the synthesis of ETAF by the keratinocytes as a function of age, with, however, a functional time-lag in favour of the keratinocytes (post-thymic lymphocyte maturation).
The thymic hormones, in particular thymulin and thymopoietin, have been used therapeutically in a large number of pharmacological and clinical studies with the aim in view of stimulating and regulating the immune defenses of the organism.
When used in the form of extracts or of molecules obtained by chemical synthesis, these products have yielded variable and disappointing results as a result of their lack of stability and a ubiquitous effect linked to the absence of dose-effect relationships.